This invention relates to heating systems and particularly relates to heating systems of the multiple condensing boiler type having improved venting and reclamation of waste exhaust heat.
Heating systems often employ multiple boiler units for providing boiler fluid, usually water, to a supply line connected to a central heating unit or to a domestic water heater or a combination of both. For example, in modern gas-fired hydronic boilers of the condensing type, sealed combustion chambers are provided with air and fuel gas. Upon firing, the combustion gas products pass downwardly over a heat exchanger containing boiler water. The heated water flows, normally in parallel, from each boiler to a common central supply line for routing to one or more heating units contiguous to the spaces to be heated or to a domestic water heating plant or both. A return line supplies water to the inlet side of each of the boilers. In such systems, the hot gases passing through the heat exchanger are cooled in water vapor condenses from the gases, releasing its latent heat of vaporization, which increases the efficiency of the heat exchanger.
In practice, any number of boiler units may comprise the heating system and each unit conventionally has its own air inlet and exhaust outlet. To provide such multiple inlets and outlets, substantial installation and construction costs are incurred. Additionally, while conventional hydronic boilers of the condensing type have increased efficiency due to utilization of the latent heat of vaporization, gas outlet exhaust temperatures still lie in a range of 110.degree. to 130.degree. F., resulting in substantial loss of heat to the system. Further, while this somewhat reduced exhaust gas temperature permits venting the exhaust gases through plastic pipe rather than through conventional chimney construction, still it has been the practice to provide individual inlets from and outlets to the atmosphere for the boilers, thus maintaining relatively high installation and construction costs.